Vacuum fuse



w. K. RANKIN Feb. 12, 1935.

VACUUM FUSE Filed Aug. 31, 1934 MAG/VES/UM 60/4750 ITIVeTTbOT William K. Rankin His Attorngg.

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Patented Feb. 12, 1935 UNITED STATES VACUUM FUSE I William K. Rankin, Lansdowne, Pa., assignor to General Electric Company, a corporation of New York Application August 31, 1934, Serial No. 742,250

7 Claims.

My invention relates to vacuum fuses, more particularly to high vacuum fuses for interrupting electric power circuits, and has for its principal object the provision of an improved vacuum fuse of the aforesaid character which shall be efficient and reliable in operation and have increased interrupting capacity.

In accordance with my invention, the metallic vapor produced by blowing of the fusible element in response to excess current is segregated with respect to the main part of the vacuum fuse casing, which may be termed the casing proper, and a vacuum gap is formed in said casing proper in series with the gap formed by blowing of the fusible element. The desirable characteristics of vacuum fuse operation including simplicity and instantaneous action are thereby obtained together with the well known insulating characteristics of a vacuum gap comparatively free of metallic vapor and gas particles.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, the single figure thereof is a view, partly in section, of a high vacuum fuse embodying my invention.

The vacuum fuse illustrated comprises an evacuated casing 1 composed, in the present instance, of a suitable insulating material, as glass, which may be readily degassed and otherwise conditioned for high vacuum fuse operation. The casing 1 may be evacuated in any well known manner, the vacuum being preferably as high as may be practicably obtained.

A fusible element as a tungsten wire or link 2 is disposed within the casing. The fusible element, which is included in the circuit to be interrupted, is connected at one end through a terminal 3 and conductor 4 to one of the fuse terminal caps 5 and at its other end to a conducting member 6 comprising a movable elec- The'electrode 6 is electrically connected through a flexible conductor 7 and a conductor 8 to the other fuse cap terminal 9.

For the purpose of segregating with respect to the casing proper the tungsten vapor produced by blowing of the element 2, a sleeve or jacket 10, preferably composed of metal, substantially encloses the fuse link. The enclosure 10 is supported at one end, as by members 11 depending from the insulating wall 12 of the casing, and is insulated with respect to the fuse terminal 5 by means of an insulating sleeve 13 surrounding the lead conductor 4. The other end of the enclosure 10 is in electrical contact at the exterior thereof with the electrode 6, the fusible element 2 extending through the opening 10' and maintaining 5 the electrode in such position.

The means for producing the vacuum gap in the casing-proper in series with the gap produced by blowing of the fusible element 2 includes resilient means, as a spring 14, connected at one 10 end, as at 15, to the terminal wire 8 and at the other end, as at 16, to the electrode 6 and normally tensioned so as to pull the electrode 6 downwardly into the casing proper when it is released by blowing of the fusible element. A large vacl5 uum gap is thereby formed in the casing proper between the enclosure 10 and the electrode 6.

The present invention has particular application to alternating current power circuits, al though not limited thereto, and the fuse terminal 20 and electrode structures are accordingly composed of a suitable low melting point metal as disclosed by Wellman et a1 Patent No. 1,934,458, granted November 7, 1933, for high vacuum fuses.

The movable electrode 6 is preferably composed of vacuum copper, i. e. copper melted in vacuum, so as to be substantially free of occluded gases and other impurities. The terminal portion 3 and the enclosure 10 are likewise preferably composed of vacuum copper, the portion 3 being coated with magnesium and the interior walls of the enclosure 10 being similarly coated to act as a getter for the purpose of absorbing traces of gas during blowing of the fusible element.

In operation excess current through the fuse causes blowing of the tungsten wire 2 and simultaneous release of the electrode 6 which is instantly snapped away from the enclosure 10 by the tension spring 14. A shield 1'? may be positioned as illustrated at one end of the fuse casing so as to protect the fuse casing from damage by the movable electrode 6.

In the interruption of alternating current power circuits a copper-to-copper break within a high vacuum has been found to be effective. It will be noted that as the fuse operates to interrupt the circuit a vacuum gap between copper terminals is formed in the fuse casing proper, the terminals constituting the enclosure 10 and movable electrode 6, the arc across the space formerly occupied by the fuse wire playing between the terminal portion 3 and enclosure 10. Accordingly, by the present arrangement the advantages of a copper-to-copper break in high vacuum are obtained and the metallic vapor produced by blowing of the fuse link is segregated with respect to said break while retaining the advantages of a tungsten wire for fuse operation.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high vacuum fuse for electric power circuits comprising an evacuated casing, a fusible element disposed in said casing, means for segregating with respect to the casing proper the metallic vapor produced by blowing of said fusible element, and means in series with said fusible element for simultaneously forming a vacuum gap in said casing proper.

2. A high vacuum fuse for electric power circuits comprising an evacuated casing, a fusible element disposed in said casing, means substantially enclosing said fusible element with respect to the fuse casing proper, and means in series with said fusible element forming a vacuum gap in said casing proper in response to blowing of said element.

3. A high vacuum fuse comprising an evacuated casing, a fusible element disposed in said casing, means substantially enclosing said fusible element for segregating the metallic vapor produced by blowing thereof with respect to the fuse casing proper, and resilient means coacting with said fusible element for actuating a movable electrode to form a vacuum gap in said casing proper, said resilient means acting in response to blowing of said fusible element.

4. A high vacuum fuse comprising an evacuated casing, a fusible element disposed in said casing, metallic enclosing structure for segregating the metallic vapor produced by blowing of said fusible element with respect to the fuse casing proper, said enclosure being insulated with respect to one terminal of said fusible element and electrically connected to the other terminal thereof, an electrode normally connected to said enclosure and last-named fuse terminal, and means forming a vacuum gap within said casing proper between said enclosure and said electrode in response toblowing of said fusible element.

5. A high vacuum fuse for alternating current power circuits comprising an evacuated casing, a fusible element disposed in said casing, means for segregating with respect to said casing proper the vapor produced by blowing of said element, and means including copper terminals in series with said element for simultaneously forming a vacuum gap in said casing proper.

6. A high vacuum fuse for electric power circuits comprising an evacuated glass casing, a

fusible element disposed in said casing, a metal-- lic enclosure for segregating with respect to the casing proper the metallic vapor produced by blowing of said element, means for insulating said enclosure with respect to one terminal of said fusible element, an electrode connected to the other terminal of said fusible element, said electrode likewise being in electrical contact with said enclosure, a flexible conductor connected to said electrode and included in the fuse circuit, and a spring normally under tension con nected to said electrode, blowing of said fusible element releasing said electrode so that a vacuum gap is formed in said casing proper.

7. A high vacuum fuse comprising an evacuated casing, a fuse link disposed in said casing, stationary and movable electrode structures normally electrically connected to one end of said fuse link, the other end of said link electrical- 1y connected to a fuse terminal, and means for causing separation of said electrode structures upon blowing of said fuse link.

WILLIAM K. RANKIN. 

